Placental Growth Factor Testing
Kelsey McLaughlin, PhD
Preeclampsia is a serious pregnancy disorder where pregnant women develop high blood pressure, leading to organ injury. It is a challenge for doctors to predict which pregnant women are at higher risk of developing preeclampsia, especially in women with no previous health or pregnancy complications.
Doctors and scientists are now investigating a new blood test to see if it is useful for the prediction of preeclampsia in pregnant women; this test measures levels of a protein called placental growth factor (PlGF) in the mother’s blood.
Keep reading to learn the science behind PlGF testing!
What is placental growth factor?
Placental growth factor (PlGF) is a protein that is produced by the placenta and released into the mother’s blood. Remember – the placenta is connected to both the mother and baby’s blood circulation.
Scientists believe that the main purpose of the placental producing PlGF in normal pregnancy is not only to help the placenta grow and develop properly, but also help the mother’s blood vessels relax and adapt to pregnancy, keeping the mother’s blood pressure at normal levels.
In normal pregnancy, levels of PlGF in the mother’s blood starts to increase in the first trimester and levels continue to rise until the third trimester. As the third trimester progresses, blood levels of PlGF begin to drop; scientists believe this may be to protect the mother against excessive bleeding at delivery.
What is the role of PlGF in preeclampsia?
Preeclampsia is a serious disorder of pregnancy, where pregnant women develop high blood pressure with organ damage. This hypertensive disorder impacts approximately 1 in 20 pregnancies and is associated with increased risk of health concerns for both mom and baby.
Scientists believe that a major cause of preeclampsia is abnormal levels of proteins produced by the placenta circulating in the mother’s blood. Women with preeclampsia commonly have some degree of placental abnormality or dysfunction. Their placentas release proteins into the mother’s blood in an abnormal manner as early as the first trimester. Abnormal levels of placental proteins can then be measured through screening blood tests.
An important study published in the New England Journal of Medicine in 2006 found that women who develop preeclampsia have much lower levels of PlGF in their blood in all trimesters, compared to women who have a normal pregnancy.
Together, this evidence led scientists to believe that PlGF could play a role in causing the development of preeclampsia. This is an example of a true bench to bedside innovation that could potentially improve the clinical care of pregnant women who are at high risk of developing preeclampsia.
How is preeclampsia currently predicted?
Currently, doctors do not have many tests to help them determine which women are at higher risk of developing preeclampsia. This means that many women will develop this condition without any warning signs.
The ability to predict which pregnant women are at higher risk of preeclampsia is important for the following reasons:
Pregnant women could have the time to discuss with doctors the potential impact and risk of preeclampsia on mom’s health and the baby’s health, including the possible need to deliver the baby prematurely.
Pregnant women could be offered therapies that potentially prevent or reduce severity of preeclampsia, such as aspirin
Pregnant women can learn more about lifestyle changes that could prevent or reduce severity of preeclampsia, such as exercise
Since PlGF levels can be tested early in pregnancy, doctors could know that a woman is at increased risk of preeclampsia many months before a woman develops high blood pressure and other clinical symptoms of preeclampsia.
What is the evidence that PlGF testing is a useful clinical tool to for predict preeclampsia?
There has been a huge amount of work invested in testing the usefulness of PlGF testing for the prediction of preeclampsia in the past 5 years.
Recent studies have determined that PlGF testing is an effective test to screen for preeclampsia in pregnant women. A recent meta-analysis reviewed 40 studies that included over 92,000 pregnant women; researchers determined that pregnant women with low PlGF have a significantly increased risk of developing preeclampsia, compared to women with normal PlGF levels. This analysis also determined that PlGF testing is most accurate after 14 weeks of pregnancy, and is the most predictive for the preeclampsia that develops before 32 - 34 weeks of pregnancy.
PlGF testing could also help doctors properly diagnose women with preeclampsia
PlGF testing has also been shown to be an effective tool to help with the diagnosis of preeclampsia. When pregnant women with preeclampsia go to the hospital and tell doctors about the symptoms they are feeling, it can sometimes be difficult for doctors to tell which women really have this disease. This is because there are many symptoms of preeclampsia, and some of them are non-specific. For example, a symptom of preeclampsia is pain in the abdomen, due to liver impairment, or headache, due to brain injury. However, many pregnant women experience abdominal pain and headaches at some point in their pregnancy, making these symptoms difficult for doctors to understand and identify quickly in the case of this disease.
Since women with preeclampsia have lower levels of PlGF, relative to heathy pregnant women, measuring levels of PlGF in the mother’s blood in women with symptoms of preeclampsia could help doctors determine which women truly have the condition versus those who do not.
A recent study by researchers in the United Kingdom determined that PlGF testing reduced the time it took doctors to diagnose women with preeclampsia; this faster diagnosis helped to decrease the complications these moms experienced from having pre-eclampsia.
Next steps for PlGF testing in Canada
PlGF testing is now officially endorsed by The National Institute for Health and Care Excellence in the United Kingdom to diagnose pregnant women with suspected preeclampsia.
Importantly, recent studies have also determined that PlGF testing is highly cost-effective, when compared to standard clinical care. PlGF testing helps to reduce the overall cost associated with appointments and pregnancy complications.
Currently, PlGF testing is not standard of care in Canadian hospitals. In fact, there are few hospitals in the world that have integrated PlGF testing into clinical practice - most centers use PlGF testing only as part of research projects. However, Canadian leaders in the obstetric field have advocated for PlGF testing to become standard of care to identify and diagnose women with preeclampsia, stating that the research evidence is highly convincing.
Further research is needed to determine how useful PlGF testing is in the real-time clinical setting for the prediction and diagnosis of preeclampsia, to build on the work done in the research setting.
Blood levels of the protein placental growth factor (PlGF) are lower in pregnant women who develop preeclampsia, compared to pregnant women who have a healthy pregnancy outcome. Recent scientific studies have shown that testing PlGF levels in the blood of pregnant women is useful to identify which women are at higher-risk of developing preeclampsia, as well as to help diagnose which women truly have preeclampsia. PlGF testing is now endorsed by The National Institute for Health and Care Excellence in the United Kingdom and is now being trialed for clinical daily use at other centers worldwide.
Every woman and every pregnancy is unique. Pregnant women should speak to their healthcare provider to ensure maternal and fetal safety. This article is meant to provide readers with current information and opinions. All medical and treatment decisions should be discussed with your healthcare provider.